access(2) using effective uid instead of real one?

Nicolas Thery nthery at
Wed Aug 12 10:43:55 PDT 2009

2009/8/11 Matthew Dillon <dillon at>:
> :It is admittedly easier and more explicit to do it as Alex and you suggest.
> :
> :To implement faccessat, which can check either real of effective ids
> :based on a flag argument, do you prefer:
> :
> :1/ Pass this "effective vs real" flag to VOP_ACCESS (either in a_mode
> :or as a new arg).
> :
> :2/ Adding a new VOP_FACCESSAT operation.
> :
> :The more general question is: can we break the VOP API (assuming we
> :change all in-tree clients)?
> :
> :Cheers,
> :Nicolas
>    Definitely (1).  I'd say just pass the new flags straight through
>    as a new argument to the base vop_access structure, but change the
>    VOP_ACCESS macro in sys/vfsops.h:
> #define VOP_ACCESS(vp, mode, cred)                      \
>        vop_access(*(vp)->v_ops, vp, mode, 0, cred)
> #define VOP_ACCESS_FLAGS(vp, mode, flags, cred)         \
>        vop_access(*(vp)->v_ops, vp, mode, flags, cred)
>     Add a new flags element to struct vop_access_args and pass and
>     initialize the new element in the vop_access() function in
>     vfs_vopops.c

Thanks Matt and Simon for the feedback.

I'll try first to refactor the various access implementations to call
vop_helper_access() if possible.

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